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Search Results: 1 - 10 of 401195 matches for " M. Potemski "
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Dirac electronic states in graphene systems: Optical spectroscopy studies
M. Orlita,M. Potemski
Physics , 2010, DOI: 10.1088/0268-1242/25/6/063001
Abstract: Electronic properties of two-dimensional allotropes of carbon, such as graphene and its bilayer, multi-layer epitaxial graphene, few-layer Bernal-stacked graphene, as well as of three-dimensional bulk graphite are reviewed from the viewpoint of recent optical spectroscopy studies. Attention is focused on relativistic-like character of quasi particles in these systems, which are referred to as massless or massive Dirac fermions.
A consistent interpretation of the low temperature magneto-transport in graphite using the Slonczewski--Weiss--McClure 3D band structure calculations
J. M. Schneider,M. Orlita,M. Potemski,D. K. Maude
Physics , 2009, DOI: 10.1103/PhysRevLett.102.166403
Abstract: Magnetotransport of natural graphite and highly oriented pyrolytic graphite (HOPG) has been measured at mK temperatures. Quantum oscillations for both electron and hole carriers are observed with orbital angular momentum quantum number up to $N\approx90$. A remarkable agreement is obtained when comparing the data and the predictions of the Slonczewski--Weiss--McClure tight binding model for massive fermions. No evidence for Dirac fermions is observed in the transport data which is dominated by the crossing of the Landau bands at the Fermi level, corresponding to $dE/dk_z=0$, which occurs away from the $H$ point where Dirac fermions are expected.
Reply to comment (arXiv:0907.2026v2) on "Consistent Interpretation of the Low-Temperature Magnetotransport in Graphite Using the Slonczewski-Weiss-McClure 3D Band-Structure Calculations" (arXiv:0902.1925)
J. M. Schneider,M. Orlita,M. Potemski,D. K. Maude
Physics , 2010,
Abstract: Reply to comment (arXiv:0907.2026v2) on "Consistent Interpretation of the Low-Temperature Magnetotransport in Graphite Using the Slonczewski-Weiss-McClure 3D Band-Structure Calculations" (arXiv:0902.1925)
Graphite from the viewpoint of Landau level spectroscopy: An effective graphene bilayer and monolayer
M. Orlita,C. Faugeras,J. M. Schneider,G. Martinez,D. K. Maude,M. Potemski
Physics , 2009, DOI: 10.1103/PhysRevLett.102.166401
Abstract: We describe an infrared transmission study of a thin layer of bulk graphite in magnetic fields up to B = 34 T. Two series of absorption lines whose energy scales as sqrtB and B are present in the spectra and identified as contributions of massless holes at the H point and massive electrons in the vicinity of the K point, respectively. We find that the optical response of the K point electrons corresponds, over a wide range of energy and magnetic field, to a graphene bilayer with an effective inter-layer coupling 2\gamma_1, twice the value for a real graphene bilayer, which reflects the crystal ordering of bulk graphite along the c-axis. The K point electrons thus behave as massive Dirac fermions with a mass enhanced twice in comparison to a true graphene bilayer.
Dirac fermions at the H point of graphite: Magneto-transmission studies
M. Orlita,C. Faugeras,G. Martinez,D. K. Maude,M. L. Sadowski,M. Potemski
Physics , 2007, DOI: 10.1103/PhysRevLett.100.136403
Abstract: We report on far infrared magneto-transmission measurements on a thin graphite sample prepared by exfoliation of highly oriented pyrolytic graphite. In magnetic field, absorption lines exhibiting a blue-shift proportional to sqrtB are observed. This is a fingerprint for massless Dirac holes at the H point in bulk graphite. The Fermi velocity is found to be c*=1.02x10^6 m/s and the pseudogap at the H point is estimated to be below 10 meV. Although the holes behave to a first approximation as a strictly 2D gas of Dirac fermions, the full 3D band structure has to be taken into account to explain all the observed spectral features.
Magneto-optical readout of dark exciton distribution in cuprous oxide
D. Fishman,C. Faugeras,M. Potemski,A. Revcolevschi,P. H. M. van Loosdrecht
Physics , 2009,
Abstract: An experimental study of the yellow exciton series in Cu2O in strong magnetic fields up to 32 T shows the optical activation of direct and phonon-assisted paraexciton luminescence due to mixing with the quadruple allowed orthoexciton state. The observed phonon-assisted luminescence yields information on the statistical distribution of occupied states. Additional time-resolved experiments provide a unique opportunity to directly determine the time evolution of the thermodynamical properties of the paraexciton gas. Because the lifetime of paraexciton is hardly affected by the optical activation in a strong magnetic field, this opens new possibilities for studies aiming at Bose-Einstein condensation of excitons in bulk semiconductors.
Resonant Rayleigh Scattering in Ordered and Intentionally Disordered Semiconductor Superlattices
V. Bellani,M. Amado,E. Diez,C. Koerdt,M. Potemski,R. Hey
Physics , 2007, DOI: 10.1103/PhysRevB.76.075349
Abstract: We report the experimental study of resonant Rayleigh scattering in GaAs-AlGaAs superlattices with ordered and intentionally disordered potential profiles (correlated and uncorrelated) in the growth direction z. We show that the intentional disorder along z modify markedly the energy dispersion of the dephasing rates of the excitons. The application of an external magnetic field in the same direction allows the continuous tuning of the in plane exciton localization and to study the interplay between the in plane and vertical disorder.
Microwave magnetoplasmon absorption by a 2DEG stripe
O. M. Fedorych,S. Moreau,M. Potemski,S. A. Studenikin,T. Saku,Y. Hirayama
Physics , 2009, DOI: 10.1142/S0217979209062219
Abstract: Microwave absorption by a high mobility 2DEG has been investigated experimentally using sensitive Electron Paramagnetic Resonance cavity technique. It is found that MW absorption spectra are chiefly governed by confined magnetoplasmon excitations in a 2DEG stripe. Spectra of the 2D magnetoplasmons are studied as a function of magnetic field, MW frequency and carrier density. The electron concentration is tuned by illumination and monitored using optical photoluminescence technique.
Optical Probing of the Spin Polarization of the nu=5/2 Quantum Hall State
M. Stern,P. Plochocka,V. Umansky,D. K. Maude,M. Potemski,I. Bar-Joseph
Physics , 2010, DOI: 10.1103/PhysRevLett.105.096801
Abstract: We apply polarization resolved photoluminescence spectroscopy to measure the spin polarization of a two dimensional electron gas in perpendicular magnetic field. In the vicinity of filling factor nu=5/2, we observe a sharp discontinuity in the energy of the zero Landau level emission line. We find that the splitting between the two circular polarizations exhibits a sharp drop at nu=5/2 and is equal to the bare Zeeman energy, which resembles the behavior at even filling factors. We show that this behavior is consistent with filling factor nu=5/2 being unpolarized.
Thermal conductivity of graphene in Corbino membrane geometry
C. Faugeras,B. Faugeras,M. Orlita,M. Potemski,R. R. Nair,A. K. Geim
Physics , 2010,
Abstract: Local laser excitation and temperature readout from the intensity ratio of Stokes to anti-Stokes Raman scattering signals are employed to study the thermal properties of a large graphene membrane. The concluded value of the heat conductivity coefficient \kappa ~ 600 W/m \cdot K is smaller than previously reported but still validates the conclusion that graphene is a very good thermal conductor.
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